Objective:To investigate the change of nodal modator 1(NOMO1) gene mRNA expression and its location during the development of rat embryonic hearts,and to explore its significance in embryonic heart development. Methods:Twenty-four pregnant Sprague-Dawley rats were randomly divided into 6 groups(n=4),embryonic hearts were obtained on the 12th,15th,16th,17th,19th,21th day in pregnancy. Real-time quantitative reverse transcription polymerase chain reaction (real-time PCR) was used to reveal NOMO1 gene mRNA expression, and fluorescence in situ hybridization(FISH) was used for its positioning analysis. Results:With the development of rat embryonic hearts,the expression levels of NOMO1 gene mRNA were from weak to strong signs of abating and its peak was on 16th day. NOMO1 gene was mainly expressed in the epicardium,while it was not detected in the myocardium,endocardium and heart valves. Conclusion:The expression of NOMO1 gene is dynamic,and it may play an important role in the fetal heart development.